1. Field of the Invention
The present invention relates to a concrete rod-like member having a seismic control structure for protecting concrete rod-like structures, such as piles, poles, towers or chimneys, placed vertically or substantially vertically in or on the earth, and buildings and constructions carried on the piles from natural disasters such as earthquakes. It also relates to a method of manufacturing such concrete rod-like structure, and a piled ring assembly used therein.
2. Prior Art
Conventionally, except for those used in nuclear facilities, for example, concrete rod-like members, such as piles, poles, towers or chimneys, placed in or on the earth are generally designed to withstand a vibrational external force (hereinafter referred to as "level 1 load") which may be probably caused by earthquakes or winds once or twice during the service life of a structure in which the concrete rod-like members are used. For the structure using such concrete rod-like members, however, the social circumstances have recently changed such that a vibrational external force (hereinafter referred to as "level 2 load") which is much less in probability of occurrence during the service life but is much greater in strength than the level 1 load, such as experienced in Hanshin-Awaji Earthquake Disaster, must not be disregarded.
Taking this into consideration, a design concept recently taken in many structures is to utilize high-strength materials or members having large cross-sectional areas to increase the design level 1 load to enhance the earthquake-proof strength of the structures. Such design concept, however, tends to pay too much cost for the least possible situation.